When should you sample manure to get the most accurate analysis? Experts at Iowa State University say that samples taken at application, or as close to it as possible, give the best results. These samples are usually well-mixed and representative of manure.
You generally won’t have results in time to make immediate adjustments in your application rate. But, you can apply the results to subsequent applications, including those involving commercial fertilizer. And the results will help create a sampling history for your manure-management plan.